A junior defence minister in the government of Edward Heath, he resigned his post and constituency in 1973 after his exposure by a Sunday newspaper.

The scandal, which also resulted in the resignation of Lord Jellicoe, the Lord Privy Seal and Leader of the Lords, echoed the Profumo affair in its titillating blend of Establishment figures, call-girls and security implications.

A man of refreshing candour who blamed no one but himself for his downfall, he explained to the television interviewer Robin Day: "People sometimes like variety. I think it's as simple as that, and I think that impulse is probably understood by almost everybody. Don't you?"

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During an interview with MI5 officers investigating a possible security breach, the recently-departed Parliamentary Under-Secretary for the Royal Air Force explained that he had resorted to a combination of "vigorous gardening" and "debauchery" as a means of dealing with stress and the "futility" of his job.

Lambton, a son of the 5th Earl of Durham who insisted on being addressed as "Lord" despite renouncing his peerage in order to remain in the House of Commons, spent most of his later life at his home in Tuscany, the Villa Cetinale.

Endowed with a considerable family fortune, he spent his time writing, entertaining and renovating the gardens. He was a friend of Prince Charles, and Tony and Cherie Blair were dining guests.

News of his death on Saturday was announced in an official notice in a local paper yesterday. Sources said it was expected that his body would be moved to Siena for a private funeral service. His daughter Lucinda Lambton, the writer and broadcaster, was thought to be in Italy yesterday.

Lord Carrington, who as Defence Secretary was Lambton's boss in 1973, said: "He was exceedingly competent and a very clever man who did his job wonderfully well."

Lord Jopling, a whip in the Heath government, described him as a very good politician, saying: "He could be extremely amusing when he spoke. It was a tragedy when he had to resign."

Elected to the seat of Berwick-upon-Tweed in 1951, Lambton was appointed PPS to Selwyn Lloyd, the Foreign Secretary, and was a hawk during the Suez crisis. Ministerial office eluded him until 1970 when Heath put him in the Ministry of Defence.

His elder brother having been killed in a shooting accident, he succeeded to the earldom of Durham that year but disclaimed the peerage to remain an MP.

A three-year battle followed during which Lambton asserted the right to use his title. It had not been resolved when the matter of call-girls intervened.

A prodigiously unfaithful husband to his wife Belinda, he had a number of mistresses and was a user of both prostitutes and drugs. Nemesis duly arrived in the shape of Norma Levy, a member of a call-girl ring servicing upper class clients.

Levy told police that her husband Colin, a conman who connived in her liaison with Lambton, was threatening to expose it. As well as compromising shots of Lambton, Levy had photos of other prominent people. Secret files released three years ago contained the names of three people but they were deleted.

The Sunday papers were not far behind the police and a picture appeared of Lambton in a three-in-a-bed session. There could be only one result. Jellicoe was collateral damage in the affair. He confessed to liaisons with call-girls after being threatened with exposure in the press.

In contrast with modern counterparts, Lambton made no excuses, saying: "I behaved with credulous stupidity and consequently have let down those I most wished to please — the Prime Minister, the Conservative Party, my electorate who have given me 22 years of loyalty, and my family."

Levy later moved to the United States. Belinda Lambton stood by her husband. She died in 2003.